[More Chapter 1]


external image volume.gifwww.grc.nasa.gov

  • SI Unit for volume is the cubic meter
  • Many chemists, however, generally use smaller units of volume like the cubic centimeter or cubic decimeter
  • Another common unit for volume is the liter. [ liter : the volume occupied by one cubic decimeter ]

-Temperature Scales

external image fig147-temperature-conversion.pngmerpower.files.wordpress.com


  • Density : mass per unit volume

Handling Numbers

-Scientific Notation

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external image scinot1.gif www.brynmawr.edu

-Significant Figures

General Guidelines for Using Significant Figures
  • Any digit that is not a zero is significant. ( 845 cm has three significant figures and 1.234 has four significant figures, and so on)
  • Zeros between nonzero digits are significant. (606 m has three significant figures 40504 kg has five significant figures, and so on)
  • Zeros to the left of the first nonzero digit are not significant. Their purpose is solely to indicate the placement of the decimal point. (0.08 L has one significant figure, 0.000045 g has two significant figures, and so on)
  • If a number is greater than one, then all zeros written to the right of the decimal point count as significant figures. (2.0 mg has two significant figures and 3.040 g has four significant figures)
  • If a number is less than one, then only the zeros that are at the end of the number and the zeros that are between the nonzero digits are significant. ( 0.090 has two significant figures, 0.00420 has three significant figures, and so on)
  • For numbers that do not contain decimal points, the trailing zeros ( that is, zeros after the last nonzero digit) may or may not be significant. (400 cm may have one significant figure (the digit 4), two significant figures (40), or three significant figures (400) ) We cannot know which is correct without more information. Using Scientific Notation, however, can prevent this ambiguity.

-Accuracy and Precision

  • Accuracy : how close a measurement is to the true value of the quantity that was measured
  • Precision : how closely two or more measurements of the same quantity agree with one another.

Dimensional Analysis in Solving Problems

external image dimensionalpracticeanswers.jpg

Dimensional Analysis : the procedure used to convert between units in solving chemistry problems
  • based on a relationship between different units that express the same physical quantity
  • in general, a relationship is used in dimensional analysis : given quantity x conversion factor = desired unit
  • units are carried through the entire sequence of calculations. (if set up correctly, then all units will cancel except the desired one)
        • all this information was extracted from the Chang Chemistry textbook